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Configuring MSTP 253
region itself. In MSTP mode, the switch ports send MSTP or STP packets (when
connected to the STP switch) and the switch provides the multiple spanning tree
function.
You can use the following command to configure the MSTP operational mode.
MSTP can intercommunicate with STP. If there is a STP switch in the switching
network, you can use the command to configure the current MSTP to run in
STP-compatible mode, otherwise, configure it to run in MSTP mode.
Perform the following configuration in system view.
Generally, if there is a STP switch on the switching network, the port connected to
it will automatically transit from MSTP mode to STP-compatible mode. The port
cannot automatically transition itself back to MSTP mode after the STP switch is
removed. In this case, you can perform the mcheck operation to transit the port to
MSTP mode by force.
By default, MSTP runs in MSTP mode.
Configuring the Bridge
Priority for a Switch
Whether or not a switch can be elected as the spanning tree root, depends on its
bridge priority. The switch configured with a lower bridge priority is more likely to
become the root. An MSTP switch can have different priorities in different STIs.
You can use the following command to configure the bridge priorities of the
designated switch in different STIs.
Perform the following configuration in system view.
When configuring the switch priority with the instance instance-id parameter,
with a value of 0, you are configuring the CIST priority of the switch.
In the process of spanning tree root election of two or more switches, with the
lowest priorities, the one has a smaller MAC address will be elected as the root.
By default, the switch priority is 32768.
Configuring the Max
Hops in an MST Region
The scale of an MST region is limited by the max hops in the MST region; which is
configured on the region root. As the BPDU travels from the spanning tree root,
Table 5 Configure the MSTP Operating Mode
Operation Command
Configure MSTP to run in STP-compatible
mode
stp mode stp
Configure MSTP to run in MSTP mode. stp mode mstp
Restore the default MSTP operating mode undo stp mode
Table 6 Configure the Priority for a Switch
Operation Command
Configure the priority of the designated
switch.
stp instance instance-id priority priority
Restore the default priority of the designated
switch.
undo stp instance instance-id priority